The present invention relates to a cooling device for a vehicle-internal battery charger and a transformer in electric vehicles.
It is generally known that a vehicle-internal battery charger is provided in electric vehicles for charging the driving battery from a 220 VAC line. In addition, known electric vehicles have a transformer that converts the relatively high voltage from the driving battery into the 12 volts that supply conventional electric vehicle equipment. Both the battery charger and the transformer exhibit a high power loss in the form of heat during operation, so that both electrical devices must be cooled. Separate cooling devices are conventionally provided for battery chargers and transformer. For example, battery chargers are usually air-cooled by being connected to a cooling panel preferably mounted outside the vehicle interior in order to avoid heat accumulation. Both air-cooled and water-cooled cooling panels are used as cooling devices for transformer. The separate cooling devices for the battery charger and the transformer contribute to an undesirable weight increase of the electric vehicle.
An object of the present invention is to improve the range of an electric vehicle by weight reduction.
This goal has been achieved in accordance with the present invention by providing that the battery charger and the transformer are mounted in a common cooling panel.
The present invention is based on the recognition that the battery charger and transformer are not operated simultaneously. The battery charger is operated only when the vehicle is standing still and plugged in. However, the transformer operates only when the vehicle is moving and electric vehicle equipment, such as lights, control devices, and windshield wipers, is switched on. Therefore, a common cooling panel need not be made larger than a cooling panel with which heretofore only the battery charger or the transformer alone was cooled.
With the device according to the present invention, both weight and space are reduced while keeping the same cooling power.
According to a presently preferred embodiment, the cooling panel is liquid-cooled to produce better cooling power than air cooling. As a result, both the battery charger and the transformer can be mounted on a common cooling panel at any desired location, not only outside the vehicle interior.
In the presently preferred embodiment, liquid cooling of the cooling panel is integrated into the cooling circuit for other components as well. Usually a coolant pump is provided to transport the coolant and can be switched on, according to the present invention, during operation of the battery charger and also when the electric vehicle is at rest. Thus, the best possible cooling is assured when the cooling requirement is increased.
The coolant pump can be switched on as a function of temperature while the battery charger is operating. For this purpose, a sensor can, for example, be mounted on the cooling panel, on the battery charger, or in the coolant. The sensor detects the temperature and directs a control unit to drive the coolant pump, with the control unit switching on the coolant pump when a temperature threshold is exceeded. With this improvement according to the invention, the coolant pump is switched on only when needed, thus saving electrical energy.
In another embodiment of the present invention, the coolant pump is also capable of being turned on as a function of time. For this purpose, by way of example, a control unit for driving the coolant pump can comprise a timer that determines the time during which the battery charger is in operation. If the operating time of the battery charger exceeds a set threshold, the coolant pump is switched on. This improvement according to the present invention also saves electrical energy since the coolant pump is only switched on when needed.